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Phase Control With Digital Delay for Circuit Tester Using Electron Beam Switching

IP.com Disclosure Number: IPCOM000083953D
Original Publication Date: 1975-Aug-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Herman, PA: AUTHOR [+2]

Abstract

Circuit devices can be tested by switching an electron beam between a point where a voltage is to be measured and a point where a reference voltage is maintained. A circuit device that is to be tested is shown with a new circuit that adjusts the phase of the beam-switching apparatus, not shown, to compensate for phase shifts that are caused by the circuit to be tested.

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Phase Control With Digital Delay for Circuit Tester Using Electron Beam Switching

Circuit devices can be tested by switching an electron beam between a point where a voltage is to be measured and a point where a reference voltage is maintained. A circuit device that is to be tested is shown with a new circuit that adjusts the phase of the beam-switching apparatus, not shown, to compensate for phase shifts that are caused by the circuit to be tested.

The output from the circuit to be tested is a voltage that alternates in level, as the beam is switched between the reference point and the voltage measuring point. This voltage is an input to a lock-in amplifier, which is switched at the frequency of a reference oscillator (not separately shown) so that the output of the amplifier is a function of the input voltage, but any drift in the direct component of the input waveform is rejected.

The output of the lock-in amplifier is applied to a compare circuit that produces an output, signifying whether the lock-in amplifier is operating ahead or behind the phase to produce zero output voltage. When this condition has been reached by adjusting the phase of the beam switching operation, a zero detect circuit signals the lock-in amplifier to shift its phase by 90 degrees so that it produces a maximum output.

The reference signal that is generated for the lock-in amplifier, is applied to a pulse former circuit that produces a narrow pulse at a zero crossing of the reference s...